NPTE-PT Test Test Equipment and Therapeutic Modalities 1 — Questions and Answers
Question 1: A physical therapist is treating a patient with acute lateral epicondylitis using therapeutic ultrasound. Which duty cycle setting would BEST minimize thermal effects while still delivering mechanical benefits to the tissue?
- 100% continuous
- 75% pulsed
- 50% pulsed
- 20% pulsed (Correct answer)
Correct answer: 20% pulsed
A 20% pulsed duty cycle (1:4 on:off ratio) minimizes heat accumulation in tissue while still delivering non-thermal mechanical effects such as cavitation and acoustic streaming. Continuous (100%) and higher duty cycles generate significant thermal effects, which are contraindicated during acute inflammation.
Question 2: During iontophoresis for calcific tendinitis, a physical therapist uses acetic acid (acetate ion, CH₃COO⁻). Under which electrode should the medication be placed?
- Anode (positive electrode), because opposite charges attract the ion into tissue
- Cathode (negative electrode), because like charges repel the ion into tissue (Correct answer)
- Either electrode, because polarity does not affect ion migration
- The dispersive pad, because it distributes current more evenly
Correct answer: Cathode (negative electrode), because like charges repel the ion into tissue
Acetic acid dissociates into the negatively charged acetate ion. In iontophoresis, ions are driven into tissue by repulsion from the same-polarity electrode. Because acetate is negative, it is placed under the cathode (negative electrode), which repels it into the underlying tissue.
Question 3: A therapist applies interferential current (IFC) using two medium-frequency carrier currents of 4,000 Hz and 4,080 Hz. What beat frequency is produced within the tissue, and which physiological effect does this range BEST target?
- 8,080 Hz — primarily used for muscle strengthening
- 80 Hz — pain modulation via gate control theory (Correct answer)
- 4,040 Hz — deep tissue heating
- 4,000 Hz — sensory nerve depolarization only
Correct answer: 80 Hz — pain modulation via gate control theory
The beat frequency in IFC equals the arithmetic difference between the two carrier frequencies (4,080 − 4,000 = 80 Hz). Beat frequencies in the 80–150 Hz range activate large-diameter Aβ sensory fibers, producing analgesia through the gate control mechanism.
Question 4: When applying a commercially prepared moist heat pack to a patient's lumbar spine, what is the recommended minimum number of towel layers between the pack and the patient's skin to prevent burns?
- 1–2 layers
- 3–4 layers
- 6–8 layers (Correct answer)
- 10–12 layers
Correct answer: 6–8 layers
Standard clinical guidelines recommend 6–8 layers of dry toweling between a hydrocollator moist heat pack and the skin. Hydrocollator packs can reach temperatures of 70–75°C (158–167°F), and this layering is necessary to reduce the surface temperature to a therapeutically safe range of approximately 40–45°C.
Question 5: A physical therapist orders whirlpool hydrotherapy for a patient with peripheral arterial disease (PAD) affecting both lower extremities. Which water temperature is MOST appropriate?
- 96–98°F (35.6–36.7°C) — near neutral warmth (Correct answer)
- 104–106°F (40–41.1°C) — mild heat
- 110°F (43.3°C) — moderate heat
- 115°F (46.1°C) — vigorous heat
Correct answer: 96–98°F (35.6–36.7°C) — near neutral warmth
Patients with PAD have impaired arterial perfusion and cannot meet elevated metabolic demands in ischemic tissue. Elevated water temperatures increase local oxygen demand while the compromised vasculature cannot increase supply, risking ischemic injury or ulceration. Near-neutral temperatures (96–98°F) allow gentle débridement benefits without imposing thermal stress.
Question 6: A therapist uses neuromuscular electrical stimulation (NMES) for quadriceps re-education two weeks after ACL reconstruction. Which on:off time ratio BEST reduces muscle fatigue while still eliciting a training contraction during early rehabilitation?
- 2:1 (twice as much on-time as off-time)
- 1:1 (equal on and off time)
- 1:3 (one second on, three seconds off)
- 1:5 (one second on, five seconds off) (Correct answer)
Correct answer: 1:5 (one second on, five seconds off)
A 1:5 on:off ratio allows five times more rest than stimulation time, which is critical in early rehabilitation when the quadriceps is deconditioned and fatigues rapidly. As strength and endurance improve, the ratio is progressively advanced toward 1:3 and then 1:1. Ratios with more on-time (2:1 or 1:1) cause rapid fatigue and reduce overall training volume.
NPTE-PT Test Test Equipment and Therapeutic Modalities 1
A physical therapist is treating a patient with acute lateral epicondylitis using therapeutic ultrasound.
Which duty cycle setting would BEST minimize thermal effects while still delivering mechanical benefits to the tissue?